The present invention relates generally to explosion barriers for mines, or the like, and more particularly to a passive explosion barrier that is responsive to relatively low velocity, as well as intermediate and high velocity explosion generated wind, but is not responsive to relatively small accidental disturbances.
In order to suppress the effects of an explosion in an underground coal mine, explosion barriers are presently employed to launch explosion suppression substances, such as water, into the path of the explosion. The explosion suppressing substance tends to cool the hot gases and avoid the spreading of coal dust ignition.
The types of explosion barriers are generally classified as being either (a) triggered or (b) passive.
Triggered barriers typically use optical and/or electronic devices to sense the flame accompanying an explosion and set off explosives or open high pressure containers to rapidly expel the explosion suppressing substance. These devices are extremely fast and are capable of setting off the barrier even before the pioneer wave of the explosion reaches the barrier. This is done by mounting the sensor between the barrier and explosion source. While generally satisfactory, triggered barriers are expensive and require a substantial amount of maintenance to insure their operation.
Passive barriers typically comprise a receptacle containing the explosion suppressing substance, such as water or dust, located on a shelf adjacent the mine roof. The shelf is formed by constructing a receiving platform beneath the mine roof. The barrier is mounted by raising the receptacle above the platform and then dropping the receptacle into the platform from above. This requires the platform to extend substantially below the mine roof and diminishes head room, especially in low roof mine galleries.
In operation, the receptacle is blown off the platform by the strong air current which precedes an explosion. The receptacle drops from the platform disbursing its contents into the path of the explosion.
While generally somewhat satisfactory for explosions causing moderate to high wind speeds (in excess of 250 ft./sec.), passive barriers are ineffective in suppressing slow moving explosions. The slow moving wind is not capable of spilling the contents of the barrier. Accordingly, the presently used passive barriers are generally located no nearer than approximately 160 ft. from the explosion source.